194 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
rise to clamped and sometimes to unclamped mycelia, while those of 
Corticium efjuscatum invariably produce unclamped mycelia. 
Oidia and chlamydospores. — The production of oidia appears to 
be confined almost entirely to the higher families of the Hymenomy- 
cetes, as was indicated by Brefeld. On the other hand the writers 
studies have demonstrated that chlamydospores are much more widely 
distributed than was previously known. Aside from Nyctalis, Fistu- 
lina, and Ptychogaster, where they occur profusely both upon the 
vegetative mycelium and upon the basidial fructification, they have 
been occasionally reported in the hymenium or other parts of the 
carpophore of several species, but have not been noted as regular and 
characteristic formations. The writer has seen no record of their 
occurrence on the vegetative mycelium save in the three genera men¬ 
tioned and in Merulius lacrymans. It has now been shown in this 
paper that they are formed regularly and abundantly on the mycelia 
of species belonging to all families of Hymenomycetes, and undoubt¬ 
edly further culture study will furnish additional evidence of their 
wide distribution. They are undoubtedly important organs of re¬ 
production in many species (see p. 149). 
Brefeld believes that oidia and chlamydospores are morphologically 
but modifications of the same structure, basing this theory largely on 
his study of Mucor racemosus (’89, p. 211-237). This species regu¬ 
larly produces cross walls in the hyphae only where the sporophores 
are to arise. The section of the mycelium that is to produce the 
sporophore may be large or very small, depending upon external con¬ 
ditions. In different culture media the hyphae may divide into thin- 
walled, barrel-shaped cells which he calls oidia, or into similar cells 
with thick walls, which he calls chlamydospores, both forms naturally * 
producing sporophores on germination. Hence in these species the 
oidium is the simpler, and the chlamydospore the somewhat more 
highly differentiated development of the same “Frucht-anlage,” or 
initial cell of the sporophore. If submerged in the substratum, instead 
of giving rise to sporophores they may function directly as spores 
and send out germ tubes. Among the Basidiomycetes although oidia 
and chlamydospores are somewhat farther separated in appearance 
and development, yet Brefeld regards both as but forms of one and 
the same structure, — “ unentwickelte Fruchttrager-Anlagen,” which 
have entirely lost their former functions, and have become physiolog¬ 
ically of the value of spores. This interpretation places oidia and 
